In the field of audio engineering, digital technology has been used most often in the design of professional equipment. Recently, consumer video cassette tape recorders have incorporated digital technology and movement toward the use of digital data in consumer audio equipment appears to be accelerating.
A major reason for this trend is that the PCM recording and playback system, which is made possible by combining a video tape recorder (VTR) and digital technology, has a much broader dynamic range than do conventional analog tape recorders. Another reason is that in comparison with those conventional recorders, the PCM system has practically no wow and flutter. Also, the frequency distortion characteristics of the PCM system are substantially superior to those of analog systems.
A PCM audio system connected to a VTR requires a digital signal processor to transform the PCM signal format to and from the appropriate television signal format. The format for the PCM audio signal may be the one prescribed by the EIAJ (Electronic Industries Association of Japan) Technical File: STC-007, which employs bit error correction schemes together with interleaving techniques. This format will be described in detail below.
The PCM audio signals are encoded in the EIAJ format for the VTR by delaying the interleaving of the data words and by adding both an error correction check word and an error detection check word. Conventional PCM signal processors for decoding the encoded PCM audio signals must include de-interleave circuits having exceedingly large storage capacities.